BEGIN

   IF NOT EXISTS (SELECT * FROM EmailsRecebidos 

                   WHERE De = @_DE

                   AND Assunto = @_ASSUNTO

                   AND Data = @_DATA)

   BEGIN

       INSERT INTO EmailsRecebidos (De, Assunto, Data)

       VALUES (@_DE, @_ASSUNTO, @_DATA)

   END

END

SELECT customer_id, first_name

FROM Customers

WHERE NOT EXISTS (

  SELECT order_id

  FROM Orders

  WHERE Orders.customer_id = Customers.customer_id

);

At first glance your original attempt seems pretty close. I'm assuming that clockDate is a DateTime fields so try this:

​

IF (NOT EXISTS(SELECT * FROM Clock WHERE cast(clockDate as date) = '08/10/2012') 

    AND userName = 'test') 

BEGIN 

    INSERT INTO Clock(clockDate, userName, breakOut) 

    VALUES(GetDate(), 'test', GetDate()) 

END 

ELSE 

BEGIN 

    UPDATE Clock 

    SET breakOut = GetDate()

    WHERE Cast(clockDate AS Date) = '08/10/2012' AND userName = 'test'

END 

Note that getdate gives you the current date. If you are trying to compare to a date (without the time) you need to cast or the time element will cause the compare to fail.

​

If clockDate is NOT datetime field (just date), then the SQL engine will do it for you - no need to cast on a set/insert statement.

​

IF (NOT EXISTS(SELECT * FROM Clock WHERE clockDate = '08/10/2012') 

    AND userName = 'test') 

BEGIN 

    INSERT INTO Clock(clockDate, userName, breakOut) 

    VALUES(GetDate(), 'test', GetDate()) 

END 

ELSE 

BEGIN 

    UPDATE Clock 

    SET breakOut = GetDate()

    WHERE clockDate = '08/10/2012' AND userName = 'test'

END 

As others have pointed out, the merge statement is another way to tackle this same logic. However, in some cases, especially with large data sets, the merge statement can be prohibitively slow, causing a lot of tran log activity. So knowing how to logic it out as shown above is still a valid technique.

-- The SQL NOT EXISTS Operator will act quite opposite to EXISTS Operator. 

-- It is used to restrict the number of rows returned by the SELECT Statement.

​

SELECT column_name

FROM table_name

WHERE NOT EXISTS (Write Subquery to Check);